• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.270-278
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• 2002

In order to reduce the exhaust emissions of a spark ignition engine, it is important not only to improve the catalyst conversion efficiency, but also to directly reduce the engine-out exhaust emissions during a cold starting of the engine and warm up periods. The purpose of this study is to evaluate feasibility of a glow plug for an early fuel evaporator. In order to promote atomization, gasoline is injected on the glow plug with room temperature(20$\^{C}$) and high temperature(250$\^{C}$). To analyze the spray behavior characteristics, a PMAS is used to measure the SMD and the dropsize distribution of an impinging spray and a free spray. Results show that the evaporation rate of the impinging spray on the high temperature surface of the glow plug was higher than that of the free spray on the room temperature surface.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.153-156
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• 2000

This paper presents an PID type fuzzy based method for nohnear engine idle controller The output is a duty cycle(DC) for driving a idle speed cont개l valve(1SCV). For precise control of SI engine, the CPS sensor and coolant temperature are used. Visual C* language is used to make simulation panel for the fast and precise idle speed control. The dSPACE board and supported Control desk program is used in experiment ta the same purpose as simulation. The experimental results have a good agreement with simulation ones.

• 대한기계학회논문집
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• 제18권10호
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• pp.2787-2796
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• 1994

The modeling of combustion process is an important part in an engine simulation program. In this study, calculated results using a conventional B-K model and the other model which is called GESIM were compared with experimentally measured data of a three-cylinder spark-ignition engine under wide range of operating conditions. The burn rates calculated from the combustion models were compared with the burn rate calculated from the one-zone heat release analysis that uses measured pressure data as an input data. As a result of the two models' comparison, the GESIM combustion model conformed to be closer to the data acquired from the experiment in wide operating ranges. The GESIM model has been improved by introducing a variable that considers the flame size, the area of flame conacting the piston surface into the model, based on the comparison between the experimental result and the calculated results. The improved combustion model predicts experimental results more precisely than that of GESIM combustion model.

• 오토저널
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• 제12권4호
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• pp.66-74
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• 1990

Friction between piston-ring assembly and cylinder wall of a spark ignition engine was evaluated under various engine operating conditions utilizing a grasshopper linkage system. The friction force was estimated by the force balance relation at the small end of connecting rod. Three forces were chosen to be measured for the objective. They were gas pressure inside the cylinder, inertia force of the piston-ring assembly, and the force exerted by the connecting rod. These forces were measured by a piezo type pressure sensor, an accelerometer and strain gauges, respectively. Comparisons were made with the frictional force evaluated by the conventional method where the assumption of constant rotational speed of engines was adopted. Due to the variation of rotational speed of engines, the conventional method was found to lead to a large error in the evaluation of the frictional force.

• 오토저널
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• 제10권6호
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• pp.85-91
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• 1988

The purpose of this study is to investigate the flow through the intake and exhaust system of a spark ignition engine. The flow was assumed to be one-dimensional, compressible and unsteady, and carburetor, muffler, valve and junction are modelled as boundary conditions according to their flow characteristics. In the experiment, four cylinder gasoline engine is used and the pressures in the intake and exhaust pipes and in the cylinder are measured and compared with the results of numerical analysis. In consequence of the comparison, four periods of pressure wave in a cycle are observed in both case of experiment and prediction. In case of exhaust pipe, the results obtained from the experiment are in accord with that from calculation. The results of the intake system show some differences with each other due to the complication in shape, but the periods of both case concur well.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.72-78
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• 1996

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated gyulsating gas flow due the working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function. back pressure, and gradient of temperature in exhaust system.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.100-106
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• 1998

The wide open throttle performance and piston temperatures were measured by the change of fuel : gasoline and liquefied petroleum gas(LPG). Bench test method was developed and experimented to study the effect of temperature on the formation of carbon deposit. The bench test results were confirmed by measuring the piston temperature and observing the deposit production rate at an actual engine running condition. Results show that if the fuel of spark ignition engine is changed from gasoline to LPG, the output power decreases about 10% and the piston temperatures increase about 40~55$^{\circ}C$. In actual engine tests, because of this temperature increase, it was observed that the quantity of carbon deposit in the top ring groove increased in a big degree. Consuquently, it is known that the fing sticking may occur if the gasoline engine was rebuilt to LPG fuelled engine. Therefore, in order to preserve the durability of LPG fuelled engine, it is necessary to lower the piston temperature by hardware modificationor to reduce the carbon deposit by the improvement of engine oil.

• 대한기계학회논문집B
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• 제28권9호
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• pp.1075-1080
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• 2004

In this study, performance and emissions characteristics of an liquefied petroleum gas (LPG) engine converted from a diesel engine were examined by using mixer system and liquid propane injection (LPi) system fuel supply methods. A compression ratio for the base diesel engine, 21, was modified into 8, 8.5, 9 and 9.5. The cylinder head and the piston crown were modified to roe the LPG in the engine. Ignition timing was controlled to be at minimum spark advance for best torque (MBT) each case. Engine performance and emissions characteristics are analyzed by investigating engine power, brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), volumetric efficiency, CO, THC and NOx. Experimental results showed that the LPi system generates higher power and lower emissions than the conventional mixer fuel supply method.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.48-55
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• 2003

The effects of pressure charge on combustion stability and emissions have been analyzed using a GDI single cylinder engine. A late injection mode of stratified condition at the air-fuel ratio of 40:1 for 1200∼2400 rpm was tested while the boosted pressure ratio was increased up to 1.5:1. In-cylinder CFD analysis was also performed for better understanding of in-cylinder flow and fuel spray behavior. With a higher boosted pressure ratio the IMEP was increased greatly due to the increased engine load, and the ISFC was improved by more than 10% at all engine speeds. The regime of stable stratified combustion was extended to a higher engine speed, but the spark ignition angle had to be more advanced for stable combustion. The emissions of ISHC and ISNOx did not show a particular trend for the increased engine speed but a general trend of lower ISHC and higher ISNOx for a gasoline engine.

• 대한기계학회논문집B
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• 제37권6호
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• pp.607-614
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• 2013

오늘날 전 세계의 자동차 회사들은 연비를 향상시키고 배기가스를 저감시키기 위해 다양한 기술을 개발하고 있다. 그 중 직접분사식 초희박 연소기술은 연료제어의 정확도를 향상시켜 연소 효율을 극대화하고 초희박 연소를 통해 연비를 향상 시킬 수 있는 차세대 기술로 평가받고 있다. 따라서 기존 가스엔진에 초희박 직접분사 기술을 적용한 초희박 LPG 직접분사 엔진을 개발하기 위해 $2{\ell}$ 급 MPI 엔진을 베이스 엔진으로 실린더 헤드를 재설계하였다. 재설계된 헤드는 초희박 연소를 구현하기 위해 인젝터와 점화플러그가 헤드 중앙에 장착되는 분무유도방식 연소시스템을 적용하였다. 연료 분사 압력별 연료 분사 시기와 점화 시기의 변경을 통해 연료 소비율과 연소 안정성을 측정하였으며 이를 통해 최적연료 분사시기와 점화시기를 선정하였다.